A group of nine concrete rectangular structures can be seen in the mud of Hoo Flats on aerial photographs taken in 1952. They are first seen on air photos taken in 1947 and may possibly have had a military function and date to the Second World War. Their location suggests that they were floated into position and they are reminiscent of some form of temporary mooring berth, though this location may mark where they were abandoned rather than where they were used. Each structure measures approximately 12.5m by 5m. They have a level surface and the majority are featureless though two have divisions running across their width. All but two of these are aligned end to end and the group forms an L-shape. Three further structures similar in length but no more than 2m wide are immediately to the west. Air photos taken in 2007 suggest that something of these structures may survive. They were mapped from aerial photographs as part of the English Heritage: Hoo Peninsula Landscape Project.